Rotator cuff tears are an extremely common injury, representing a significant source of pain and disability. Many tears are treated nonoperatively, while others undergo surgery either early or following a period of non-operative management. The likelihood of certain tears to progress, which might dictate surgical repair early, even in a patient who becomes asymptomatic, is not well understood. The local strain environment within a rotator cuff tendon is a critical factor for initiation and progression of rotator cuff tendon tears. Therefore, we have developed a novel, non-contact, non-invasive, method using magnetic resonance imaging coupled with digital texture correlation techniques in cadaver shoulders in an in situ loaded biomechanical model to quantify two-dimensional strain fields and their changes which might serve to predict regions at risk for failure and tear progression. This approach will be used for the current study. The objective of the current study is to rigorously quantify strain fields, both direction and magnitude, in the rotator cuff tendon in normal, torn, and repaired states to test hypotheses concerning strain alterations due to rotator cuff dysfunction. In addition, the structural organization of the rotator cuff will be studied with respect to rotator cuff strain distributions. The Specific Aims are to: 1) Quantify strain fields resulting from articular side and bursal side partial thickness and full thickness supraspinatus tendon tears, 2) Quantify strain fields in the repaired supraspinatus tendon adjacent to the tear location, and 3) Quantify fiber orientations throughout the complete supraspinatus tendon. These studies will lend significant insight into the pathogenesis and progression of specific rotator cuff tears, as well as provide a scientific basis for cuff tear management clinically. Future studies will develop a mathematical model of the cuff to predict tissue stresses. In addition, future studies will advance both to a three-dimensional analysis and to evaluation of the in vivo state, both in animal and in human, to address hypotheses on the role of rotator cuff degeneration, remodeling, and healing over time.